Assessing the Impacts of Land Use and Land Cover-Based Drought Adaptation Measures with an Eco-Hydrological Model

Abstract. Europe has warmed by about 1.5 °C above pre-industrial levels and endured record-breaking droughts from 2018–2020, underscoring the need for adaptation to water scarcity. This study examines the potential of targeted land use and land cover (LULC) changes to modify water fluxes and soil moisture storage for greater hydrologic drought resilience. Evaluated measures comprise replacing grain corn with sorghum on agricultural fields, converting coniferous forests (spruce, pine) to broadleaved stands (beech, oak), and mitigating imperviousness in built-up areas.

The study area, the 1,983 km² Upper Lippe catchment in Germany, and the exceptionally dry period of 2011–2020, are suitable conditions to address the research question for a temperate region. The assessment was conducted with the eco-hydrological model SWAT+ and novel approaches were implemented to accurately parameterize agricultural land use and management, dominant tree species, and the realistic impervious fraction of built-up areas within the model using publicly available existing data products and studies. After applying a calibration strategy that specifically targeted low-flow periods, the model performs well in the study period combining a good representation of low-flow periods with a standardized Root Mean Square Error for flows exceeding a 70 % probability threshold of 0.14 and while also maintaining robust overall streamflow dynamics with a modified Kling-Gupta Efficiency (KGE’) of 0.90 at the catchment outlet. The parameterization and calibration approaches can serve as references for model setups addressing similar ecoregions and research questions.

In the adapted agricultural areas, the evapotranspiration coefficient decreased by -11.7 percentage points (pp, area weighted median of the annual average) with reductions concentrated in the vegetation period leading to increases in soil moisture content. In response, the drainage flow coefficient increased by +3.3 pp with increases concentrated in the winter months and the groundwater recharge coefficient increased by +4.8 pp with a relatively uniform distribution throughout the year. The evapotranspiration coefficient from the adapted forested areas was reduced by -15.9 pp (from 67.5 %) with reductions occurring outside of the summer months. Here, increased soil moisture content increases the lateral flow coefficient by +9.0 pp and the groundwater recharge coefficient by 3.8 pp. Surface runoff increases only slightly, with enhanced surface runoff primarily occurring in mountainous areas where broadleaf trees provide less rainfall interception during winter dormancy. In the adapted built-up areas, reductions in impervious surfaces led to an increased groundwater recharge coefficient (+0.4 pp) and a decreased surface runoff coefficient (-3.6 pp), while the evapotranspiration coefficient increased (+2 pp), particularly in summer. Plant-available moisture in the topsoil increased in the adapted agricultural and forested areas across all modeled adaptation measures, reducing magnitude and duration of water stressed periods. These results demonstrate that LULC adaptations can shift landscape water balance by reducing evapotranspiration and increasing infiltration, thereby strengthening drought resilience and offering co‑benefits such as urban cooling. Such insights can guide policy and land management toward scalable, land use‑based solutions for extreme weather resilience under a warming global climate.